1. Field of the Invention
This invention relates generally to emulsion treating, and, more particularly, to an emulsion treating apparatus and method which enables a plurality of distributors to be externally adjusted to more accurately control the treatment of the emulsion flowing through the treater.
2. Description of Related Art
Petroleum as it is naturally produced from an underground formation, is, in most cases, a mechanical mixture of oil, entrained gas and produced water, some of which latter may be present as an oil/produced water emulsion. It is desirable, and usually necessary to treat the petroleum thus produced at the wellhead, for the separation and removal of the entrained gas and emulsified produced water, in order to render the oil pipelinable. Usually, the separated produced water (salt water, heavy mineralized water or fresh water) is pumped back into the formation, in order to assist in maintaining the pressure therein, and also to resolve the produced water disposal problem. Separated gas is vented or flared, if in small quantities, and if in commercial volumes, is delivered to a pipeline for distribution. The equipment used for this three-phase separation is known as a treater, and is generally quite familiar to those whom the present invention will be addressed.
Such treaters normally involve the heating of the produced petroleum, in order to lower the viscosity of the fluid phase, and also to assist in the separation of the entrained gas. Brine droplets are coalesced either mechanically, as by forcing the emulsion through a series of perforated baffles; or electrostatically, as by forcing the emulsion through a highenergy, electrically charged field; or chemically, by means of surface-active chemical agents which reduce the surface tension on the water droplets, thereby allowing them to coalesce into larger drops for separation by gravity. Frequently, two or more coalescing methods are employed in a treater.
Treaters have evolved in design from early developed open vats, which maintained the produced petroleum in stationary condition for several days, permitting the produced water to separate to the bottom of the vat by gravity. There evolved heating methods in order to expedite the treatment by reducing the viscosity of the oil, as described. Subsequent development evolved the heater-treater which is the current state-of-the-art comprising an elongated enclosed tank having a burner-fired heater section and a downstream treater section for continuous flow, with a series of perforated baffles positioned within the treater section transversely to the flow of fluids; the perforated baffles function to promote the even distribution over the full cross-sectional area of the treater section of the fluids in motion, and to cause a pressure drop within the fluid across the perforated baffles which results in a release of entrained gasses, which then collect in the upper volume of the tank for removal. However, produced water emulsions within the oil have continued to be inefficiently treated by gravity settling and baffling of the flow following heating; thus, further measures have been necessary in order to cause coalescing of the small droplets of produced water into larger drops which could be settled out by gravity.
The conventional treatment has the operational disadvantages of being time-consuming, due the residence time required in the treater and the requirement that the petroleum be heated to a sufficiently high temperature to reduce the viscosity thereof so that coalescing of the emulsified droplets will be encouraged. The maintenance of a large quantity of oil at a relatively high temperature is costly of energy, and requires the equipment involved to be capable of sustained operation at the temperatures involved.
Treaters in current use are normally tanks in the form of elongated, horizontal cylinders divided by means of internal partitions into compartments through which the petroleum will sequentially flow. Burner-fired heaters are normally include in the upstream heater section for heating the emulsion to the desired temperature, during which most of the entrained gas and some of the brine will separate from the emulsion. The partially-de-emulsified brine then flows into a treater section, in substantially gas-free state, encountering a series of baffles adapted to encourage even flow of fluids and to avoid the formation of flow channels within the fluid body, thereby to assist in separation of remaining gases and coalescing of produced water droplets, and their separation by gravity to the bottom of the tank for ultimate discharge removal.
Various techniques of improvement have heretofore been employed in order to minimize treatment time and heat energy consumption. In U.S. Pat. No. 4,329,159 to Bull, there is described a method and apparatus of the type described, additionally including a number of metallic apertured grid electrodes suspended adjacent apertured baffles, the electrodes being supplied with electrical energy. A series of longitudinally spaced electrical fields of high potential and density are thereby created, which cause droplets of emulsified brine to move in violent random fashion, the droplets coalescing and collecting into drops of sufficient weight so as to fall by gravity to the lower portion of the treater water phase section for removal.
While the addition of the electrostatic elements described in U.S. Pat. No. 4,329,159 resulted in enhanced separation of the oil and brine, a further improvement to this patent was set forth in U.S. Pat. No. 4,919,777 to Bull, in which a series of coalescer or collector elements are positioned within the treater compartment, each in immediate downstream relationship from an electrostatic element, the coalescer element being electrically grounded to the tank thereby causing the brine droplets to be attracted to the coalescer element where coalescing into brine drops occurs, followed by gravity collection and removal.
Even when electricity is not economically available, the U.S. Pat. No. 4,919,777 patent operates as a mechanical (non-electrostatic) treater in which a brine de-emulsifying element consisting of a bundle of open-ended tubes having foreshortened vertical dimensions positioned downwardly inclined in the direction of flow. Individual tubes present opposition to the flow of emulsion for contact between the brine droplets of the emulsion and the interior surfaces for accumulation and downward trickling by gravity to a sump for collection and removal. Each such tube having a diameter of approximately one inch and a length of approximately one foot, brine droplets moving forwardly with the emulsion and passing through the open-ended passages of the collector elements will be separated from the emulsion by contact with and adhesion to the interior surfaces of the tubes. Contact with a surface of one of such tubes will be facilitated in accordance with Stokes Law of Fluid Flow.
The present invention provides a still further improvement to those disclosed above, resulting in enhanced separation of oil from brine in an emulsion, by replacing the perforated baffles with externally operated, adjustable, vertical louvered distribution baffles which can accommodate a wide range of crude oils, operating at various pressures and temperatures, under a wide variety of flow conditions.
In presently existing equipment, if a different viscosity oil having varying produced water content is to be treated, or if the existing equipment becomes clogged or is somehow rendered inoperative, the equipment must be shut down, allowed to cool off, opened and then cleaned or new components installed, under stringent environmental and safety constraints. Such shutdowns are expensive and time consuming, and, therefore, needed adjustments, cleaning, and/or required service, are often put-off, thereby producing undesirable results, and subjecting the equipment to unneeded stress and breakdowns.
In the method and apparatus of the present invention, externally adjustable, vertical louvered baffles or distributors replace the perforated baffles in the treater section, and are suspended in the emulsion downstream or upstream of any electrostatic grid and upstream of any coalescer elements, to more accurately control the flow of emulsion as it moves through the treater section.